Manufacturing Process Of Compound Fertilizer



There are some process of manufacturing of Compound Fertilizer. We can get two different sizes fertilizer from these process.

Normal/Regular Size:

i) Steam or water granulation

Granular Size:
ii) Chemical granulation
iii) Drop formation (Prilling)
v) Dry mixing/Blending
iv) Compaction granulation

i) Steam/Water granulation:

In the steam/water granulation process, compound fertilizers are formed by agglomeration. The solid raw materials are proportioned and usually premixed before being fed to the granulator where granulator where agglomeration is initiated. In the granulator (usually a rotary drum) steam and/or water is added to provide sufficient liquid phase and plasticity to cause the dry raw materials to agglomerate into product size. The moist and plastic granules are dried usually in a rotary drum type, fuel fired dryer and screened to remove the product size fraction. If we add 50% Nitrogen, 40% Phosphorus, then we’ll add 10% of additive/filler. Mixing of two/three raw materials in a place is called pre-mix.

                                           Figure: Flow diagram of Steam/Water Granulation

ii) Chemical Granulation:

Chemical granulation is the most complex method for preparing compound fertilizers. The chemical granulation process is very similar to the previously described steam/water granulation process except that most of the liquid phase required to achieve granulation is obtained by various chemical reactions such as:

i) Ca(H2PO4)2.H2O+(NH4)2SO4+H2O = CaSO4.2H2O+2NH4H2PO4
ii) (NH4)2SO4+2KCl = K2SO4+2NH4Cl
iii) NH4NO3+KCl = KNO3+NH4Cl
iv) (NH4)2SO4+CaSO4+H2O = (NH4)2SO4.CaSO4.H2O
v) K2SO4+CaSO4+H2O = K2SO4.CaSO4.H2O
vi) H3PO4+(NH4)2HPO4 = 2NH4H2PO4
vii) Ca(H2PO4)2.H2O+4CO(NH2)2 = Ca(H2PO4)2.4CO(NH2)2+H2O

Note: iv, v & vi no. show additive reactions.

iii) Drop formation (Prilling):


In this process, the fertilizer mixture solution is concentrated to approximately 96-98% solids before it is introduced to the top of the prilling tower through prilling bucket. The prilling bucket are designed to produce droplets of the molten fertilizer mixture that upon solidification, will yield the desired granule (prill) size.

                              
                              Figure: Flowchart/flow diagram of drop formation (prilling)

iv) Compaction granulation:

In this process, mechanical force is used to form dense particle from finely divided (non-granular) solid material. With compaction granulation, the dry materials are first proportioned and mixed to achieve desired nutrient ratio. The mixture is then fed to a pressure poll compaction machine that forms the powdered material into a dense hard sheet of about 2-3 cm thick and 60-100 cm wide. The compacted sheet is then crushed in a controlled manner to form smaller particles. The crushed material is screened to obtain the desired product size.

iv) Dry mixing (Blending):


      Figure: Flow diagram of manufacturing of compound fertilizer by fertilizer blending plant
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